sum.cpp

#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>

#include <iostream>
#include <string>
#include <numeric>

namespace client
{

namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace phoenix = boost::phoenix;

template <typename Iterator>
const
qi::rule<Iterator,
         std::vector<double>(),
         ascii::space_type>
parse_nums(const std::string& delim)
{
    return qi::eps [qi::_val = phoenix::construct<std::vector<double>>()]
        >> qi::double_ [phoenix::push_back(qi::_val, qi::_1)]
        >> *(qi::lit(delim) >> qi::double_ [phoenix::push_back(qi::_val, qi::_1)]);
}

}

int main()
{
    std::string buffer;
    while (std::getline(std::cin, buffer))
    {
        if (buffer == "bye")
            break;
        std::vector<double> result;
        auto iter = buffer.begin();
        if (boost::spirit::qi::phrase_parse(
            iter, buffer.end(),
            client::parse_nums<decltype(iter)>(","),
            boost::spirit::ascii::space,
            result))
        {
            std::cout << "sum = " <<
                         std::accumulate(
                             result.begin(),
                             result.end(),
                             0.0,
                             [](const auto& x, const auto& y){ return x + y; })
                      << std::endl;
        }
        else
        {
            std::cerr << "Failed to parse." << std::endl;
        }
    }
    return 0;
}